Dental impression composition



Patented Aug. 5, 1947 DENTAL IMPRESSION COMPOSITION Stanley E. Noyes,Los Angeles, Calif.

No Drawing. Application April 30, 1945, Serial No. 591,221

7 Claims. (01. 18-47) This invention relates to a new dental impressioncompound and the method of producing the same.

For many dental purposes such as making of full dentures, partialdentures, bridges, etc., it is necessary for the dentist to be able toaccurately reproduce portions of the mouth of the subject. Suchreproductions often involve the duplication of undercuts of more or lessseverity, as for instance in the case where a tooth or teeth have beenextracted and the adjacent teeth have crowded together.

For many years dental impressions have been taken with materials such asplaster of Paris, or various shellac or wax compositions. Thesematerials have little or no elasticity and. while it is not difficult totake some impressions with them, such as for most full dentures, it isnot possible to reproduce accurately undercuts without either breakingthe impression and i e-assembling it as is done with plaster, or takingthe impression in sections as is the practice in the use ofshellac andWax compounds. The foregoing methods obviously involve time and there isthe danger of inaccuracy, as well as discomfort to the patient.

By the use of an impression material which may be introduced in themouth in a fluid or plastic condition and cooled to an elastic state, itis possible to take an impression which will accurately reproduce alldetails of the portion of the mouth under examination, and which due toits elasticity, can be removed from any undercuts present without losingthe accuracy of the impression.

Due to the narrow range of temperature which the human mouth can stand,rather strict limitations are placed on the types of elastic materialswhich can be used. These materials must obviously be either fluid orplastic when they are seated to place in the mouth and must change bycooling to an elastic gel which will permit removal from the undercutswithout permanent distortion. They must also either harden to a solid orbe a sufficiently tough and rigid gel so that they may be used as moldsfor models of plaster or other compounds to be poured into them.

My dental impression material is composed of a suitable gel formingagent which may be obtained, for example, from the various marine algaein-'- cluding gigartina, chondrus, bladder wrack, kelp, gracilaria, oragar-agar. If the gel forming agent is alginic acid it may be convertedinto the form 'of a salt, as for example, sodium alginate, potassiumalginate, ammonium alginate or mixtures thereof. The salts of alginicacid are used in the impression material to render the product elastic.

To the gel forming agent then is added a heavy metal silicate such asfor example lead silicate or zinc silicate. The exact chemical reactionwhich takes place on the addition of the lead or zinc silicate to thedental composition is not fully understood but it is definitely known toaffect the conversion of the gel forming agent from the soluble to theinsoluble form. For example water soluble alkali metal salts of alginicacid are converted over to the insoluble form.

To the foregoing composition then is also added a water solublephosphate such as sodium, potassium or lithium phosphate sodiumhexametaphosphate may also be employed. Sodium tetrapyrophosphate hasalso been found to be especially satisfactory by reason of its limitedsolubility in Water.

To the foregoing composition then is also added sodium fiuosilicate,however other silico fluorides may be used as for example zinc,manganese, or calcium.

Zinc nitrate is also added to my composition to produce an insolublecompound with the gel forming constituents such as the alginates. Theordinary commercia] U. S. P. zinc nitrate may be used but in order tocontrol the action of the zinc nitrate it has been found advantageous topretreat the zinc nitrate in the following manner. The zinc nitrate isfirst dissolved in a low boiling aliphatic alcohol such as ethyl ormethyl alcohol and this solution is evaporated at a temperature of about200 F. until all of the alcohol present has been vaporized. Theresulting residue is then Water Washed, dried and ground. Again it isnot understood exactly why the zinc nitrate pretreated in the abovemanner is aliected. It is definitely known, however, that the Zincnitrate pretreated with alcohol, as described above is less watersoluble and reacts more slowly with the gel forming agent (for examplesodium or potassium alginate).

To the above composition there is finally added a filler such asdiatomaceous earth, manganese carbonate, or talc which is insoluble inwater and which is easily Wetted.

The following is a specific example of my new dental composition: 10grams of diatomaceous earth, 1.75 grams of sodium fluosilicate, 4.0grams of sodium or potassium alginate, 6.75 grams of lead silicate, 0.5gram of sodium tetrapyrophosphate and 0.5 gram of zinc nitrate (eitheras purchased in the U. S. P. form or pretreated with alcohol asdescribed above) are placed in a finely divided and dry form in atumbling keg or mixer and mixed until a uniform blend is obtained. Thismixing should be so conducted that the temperature in the tumbler ormixing device does not exceed 100 to 110 F., otherwise the finalcomposition may be damaged. The blended material is then withdrawn fromthe tumbling or mixing device and thoroughly mixed with 50 cubiccentimeters of water with a spatula until, a smooth creamy mixture isobtained which sets in a short time to an elastic gel. In practice thiscreamy mixture is placed in a dental tray which is placed in the mouthof the patient where it sets up in the form of the elastic gel in fromthree to six minutes. The setting time can be varied by varying thetemperature of the Water used. Cold water will retard the set and warmwater will hasten it. This control can also be maintained by varying theamount of the powdered composition used in combination with water. Thegreater amount of powder used in relationshi to the water the more timewill be required to obtain the proper set.

An impression containing the above composition can be removed from themouth after setting without breaking, tearing or distorting and willallow dental stone or plaster of Paris to set hard against its surfacewith extreme accuracy. This impression material also possesses thequality of not requiring a separating medium or fixing bath beforepouring dental stone or plaster of Paris into the impression.Furthermore, it can be stored over a long period without deteriorating.

The specific mixture of ingredients set forth above in the example canbe modified without departing from the spirit of the invention.

I claim:

1. A composition of matter comprising an alkali metal alginate, leadsilicate and zinc nitrate, which has been dissolved in a lower aliphaticalcohol and recovered therefrom by evaporation of the alcohol.

2. A composition of matter comprising an alkali metal alginate, leadsilicate, sodium fiuosilicate and zinc nitrate which has been renderedsubstantitally insoluble in water by treatment with a lower aliphaticalcohol.

3. A composition of matter comprising an alkali metal alginate, leadsilicate, sodium fluosilicate, an inorganic phosphate salt, and zincnitrate which has been dissolved in ethyl alcohol and recoveredtherefrom by evaporation of the alcohol.

4. A composition of matter comprising an alkali metal alginate, leadsilicate and zinc nitrate which is substantially insoluble in water.

5. A composition of matter comprising a gel forming material selectedfrom the class consistingof alginates and agar-agar, lead silicate andzinc nitrate which has been dissolved in ethyl alcohol and recoveredtherefrom by evaporation of the alcohol.

6. A composition of matter comprising an alkali metal alginate, a heavymetal silicate, and zinc nitrate which has been dissolved in ethylalcohol and recovered therefrom by evaporation of the alcohol.

7. A composition of matter comprising an alkali metal alginate, a heavymetal silicate, sodium fiuosilicate, sodium tetra pyrophosphate a fillerand zinc nitrate which has been dissolved in ethyl alcohol and recoveredtherefrom by evaporation of the alcohol at a temperature notsubstantially in excess of 200 F.

STANLEY E. NOYES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,249,694 Wilding July 15, 19412,298,835 Noyes Oct. 13, 1942 2,325,051 Gross July 2'7, 1943

